netdev - Re: [PATCH net 2/2] fsl/fman: Fix refcount handling of fman-related devices

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Message-ID: <a0aec660-c18b-4d85-b85b-58fce3668e64@redhat.com>
Date: Thu, 17 Oct 2024 12:01:01 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Aleksandr Mishin <amishin@...rgos.ru>,
 Igal Liberman <igal.liberman@...escale.com>
Cc: Simon Horman <horms@...nel.org>, Madalin Bucur <madalin.bucur@....com>,
 Sean Anderson <sean.anderson@...o.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH net 2/2] fsl/fman: Fix refcount handling of fman-related
 devices

On 10/15/24 08:01, Aleksandr Mishin wrote:
> In mac_probe() there are multiple calls to of_find_device_by_node(),
> fman_bind() and fman_port_bind() which takes references to of_dev->dev.
> Not all references taken by these calls are released later on error path
> in mac_probe() and in mac_remove() which lead to reference leaks.
> 
> Add references release.
> 
> Fixes: 3933961682a3 ("fsl/fman: Add FMan MAC driver")
> Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
> ---
> Compile tested only.
> 
>   drivers/net/ethernet/freescale/fman/mac.c | 62 +++++++++++++++++------
>   1 file changed, 47 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fman/mac.c b/drivers/net/ethernet/freescale/fman/mac.c
> index 9b863db0bf08..11da139082e1 100644
> --- a/drivers/net/ethernet/freescale/fman/mac.c
> +++ b/drivers/net/ethernet/freescale/fman/mac.c
> @@ -204,7 +204,7 @@ static int mac_probe(struct platform_device *_of_dev)
>   	if (err) {
>   		dev_err(dev, "failed to read cell-index for %pOF\n", dev_node);
>   		err = -EINVAL;
> -		goto _return_of_node_put;
> +		goto _return_dev_put;

We are after a succesful of_find_device_by_node and prior to 
fman_bind(), mac_dev->fman_dev refcount is 1

> @@ -213,40 +213,51 @@ static int mac_probe(struct platform_device *_of_dev)
>   	if (!priv->fman) {
>   		dev_err(dev, "fman_bind(%pOF) failed\n", dev_node);
>   		err = -ENODEV;
> -		goto _return_of_node_put;
> +		goto _return_dev_put;
>   	}
>   
> +	/* Two references have been taken in of_find_device_by_node()
> +	 * and fman_bind(). Release one of them here. The second one
> +	 * will be released in mac_remove().
> +	 */
> +	put_device(mac_dev->fman_dev);
>   	of_node_put(dev_node);
> +	dev_node = NULL;
>   
>   	/* Get the address of the memory mapped registers */
>   	mac_dev->res = platform_get_mem_or_io(_of_dev, 0);
>   	if (!mac_dev->res) {
>   		dev_err(dev, "could not get registers\n");
> -		return -EINVAL;
> +		err = -EINVAL;
> +		goto _return_dev_put;

Here we are after a successful fman_bind(), mac_dev->fman_dev  refcount 
is 2. _return_dev_put will drop a single reference, this error path 
looks buggy.

Similar issue for the _return_dev_arr_put error path below.

Cheers,

Paolo